Add tests to ensure that we remove the Strong Password decoration when the text field's type changes.

Extract code to toggle showing the AutoFill button from fast/forms/auto-fill-button/input-{disabled, readonly}-strong-password-and-strong-confirmation-password-auto-fill-buttons.html
into a new file fast/forms/auto-fill-button/resources/process-auto-fill-button-type-and-invoke-runTest.js
that can be shared.